Assessment of climate change impacts on water quantity and quality of the multi-river Vistula Lagoon catchment

Figures & data

Table 1 GCM/RCM combination matrix of the climate scenarios used in this study for climate impact assessment.

GCM
Institute_RCM	HadCM 3Q0	HadCM 3Q3	HadCM 3Q16	ECHAM5-r3	BCM	ARPEGE
C4l_RCA3			S5
HC_HadRM3Q0	S2
HC_HadRM3Q3		S3
HC_HadRM3Q16			S4
ETHZ_CLM	S6
KNMI_RACMO2				S7
SMHI_RCA3		S1		S9	S8
MPI_REMO				S10
CNRM_AladinRM51						S11
DMI_HIRHAM5				S13	S14	S12
ICTP_REgCM3				S15

Fig. 1 Overview map of the Vistula Lagoon catchment showing the digital elevation model (DEM), national borders, major sub-catchments (numbered), main river courses, discharge gauges with available data, as well as the grid points of WATCH climate data.

Table 2 Total amounts of point-source nutrient inputs and fertilization rates implemented in the model.

Nutrient source	Nitrogen	Phosphorus
Point sources (kg d^-1)
Pasleka basin	341	76
Mamonovka basin	71	14
Remainder of catchment	6598	1294
Fertilization (kg ha^-1)
Total agricultural area	72	16

Fig. 2 Performance of SWIM calculated for the total period and distinguished into calibration/validation periods for the two main rivers flowing to the Vistula Lagoon: Comparison of simulated and observed discharges as daily (left) and long-term average daily (right) dynamics for the Pasleka and Pregolya rivers.

Table 3 Model performances at 10 discharge gauges located within the Vistula Lagoon catchment achieved by using the SWIM model covering the entire drainage area with a common parameter set.

River	Pissa	Angrapa	Pregolya	Lava	Mamonovka	Pasleka	Bauda	Pasleka	Waska	Dzierzgon
Gauge	Zeleny Bor	Berestvo	Gvardeysk	Rodniki	Mamonovo	Nowa Pasleka	Nowe Sadulki	Lozy	Paslek	Bagart
	(1995–2000)	(1995–2000)	(1983–1996)	(1995–2000)	(2008–2009*)	(1998–2000*)	(2009)	(2007–2009)	(2009)	(2009)
NSE	0.73	0.63	0.70	0.70	0.62	0.72	0.55	0.66	0.48	0.34
DB	0.4	−23.6	0.6	−7.3	−29.6	−9.2	−6.8	12.9	−9.8	−7.4

* Monthly values

Fig. 3 Comparison of the observed (general mean discharge values found in literature, grey) and simulated (average values obtained with SWIM for 1980–2009, white) water inputs to the Vistula Lagoon per river and in total.

Fig. 4 Observed (obs) and simulated (sim) water quality variables for the Pasleka River (gauge Nowa Pasleka): monthly averages (left) and long-term average seasonal dynamics (right) of nitrate nitrogen (NO₃-N), ammonium nitrogen (NH₄-N), phosphate phosphorus (PO₄-P), and dissolved oxygen (DO) concentrations, as well as water temperature for the period 2005–2009; the long-term average seasonal nutrient dynamics could be also compared with the SWIM simulated average monthly discharge (Q_sim) at the same gauge.

Table 4 Spatial validation of water quality variables for nine rivers flowing into the Vistula Lagoon: comparison of the average of all available observed nutrient and dissolved oxygen (DO) concentrations with the average of the corresponding simulated values for the period 1998–2000 and some additional sub-periods in 1980–2009.

	Prokhladnaya	Vileyka	Mamonovka	Pasleka	Bauda	Nogat	Elblag	Nelma	Pregolya
Period	1998–2000
Additional period			2008–2009	2005–2009					1980–1987
NO3-N (mg L^-1)
Obs	0.68	0.68	0.67	1.16	1.29	1.07	1.33	0.68	0.77
Sim	1.05	1.31	0.74	1.44	1.42	1.12	2.14	0.70	1.26
NH4-N (mg L^-1)
Obs	0.21	0.21	0.37	0.38	0.45	0.58	0.83	0.21	0.69
Sim	0.26	0.40	0.36	0.35	0.41	0.50	0.83	0.30	0.82
PO4-P (mg L^-1)
Obs	0.05	0.05	0.09	0.11	0.17	0.08	0.16	0.05	0.08
Sim	0.05	0.11	0.08	0.11	0.15	0.09	0.24	0.05	0.13
DO (mg L^-1)
Obs	10.56	10.56	9.72	8.70	10.16	9.54	9.47	10.56	6.40
Sim	10.37	9.85	10.04	10.05	9.94	9.60	8.80	10.30	9.16

Table 5 Average daily nutrient loads of the 12 largest rivers entering Vistula Lagoon, as simulated with SWIM for the calibration/validation period 1980–2009.

	NO3-N (kg d^-1)	NH4-N (kg d^-1)	PO4-P (kg d^-1)
Polish rivers total	5534	1673	329
Szkarpawa	418	133	26
Nogat	830	362	65
Elblag	1284	411	103
Bauda	288	87	16
Pasleka	2714	679	119
Russian rivers total	8418	4892	540
Mamonovka	211	95	14
Vileyka	45	9	2
Prokhladnaya	1026	283	29
Pregolya	6866	4374	480
Grayevka	45	27	2
Nelma	119	55	8
Primorskaya	106	50	4

Table 6 Annual climate change signals for the Vistula Lagoon catchment as the average of all 15 ENSEMBLES scenarios.

	Temperature (°C)			Precipitation (%)
	p1–p0	p2–p0	p3–p0	p1–p0	p2–p0	p3–p0
Climate change signal	+1.05	+2.18	+3.12	+4.3	+10.5	+9.7

Fig. 5 Climate change signals for all 15 ENSEMBLES scenarios and on average calculated as the differences between the average annual precipitation and temperature, respectively, of the three future periods (p1, p2, p3) to the average annual values of the reference period (p0) of the same scenario.

Fig. 6 Dynamics of total water inflow to the Vistula Lagoon averaged for simulations driven by 15 ENSEMBLES climate scenarios: (left) long-term average daily discharges with percentile bands simulated in future periods compared to the long-term average daily discharge simulated in the reference period driven by simulated climate; and (right) absolute difference in monthly average discharges of three future periods compared to those simulated in the reference period 1971–2000. See text for explanation.

Fig. 7 Impact of ENSEMBLES climate change scenarios on water quality parameters and nutrient loads coming into the Vistula Lagoon: average absolute changes in seasonal dynamics of water temperature (T_wat), dissolved oxygen (DO), nitrate nitrogen (NO₃-N), ammonium nitrogen (NH₄-N) and phosphate phosphorus (PO₄-P) calculated as the difference between SWIM-simulated mean monthly nutrient outputs under future climate conditions compared to results achieved under the simulated climate in the reference period.

Fig. 8 Ranges of percentage changes of total discharge and nutrient inputs to the Vistula Lagoon as well as of average water temperatures and dissolved oxygen concentrations simulated with SWIM driven by 15 ENSEMBLES climate scenarios (future periods (p1, p2, p3) compared to reference period (p0) of the same scenario). The box plots visualize the following ranges: min/max, 25/75-percentile, median and average (dots).

Fig. 9 Spatial variability of projected climate change impacts on water discharge (Q), nitrate nitrogen loads (NO₃-N), ammonium nitrogen loads (NH₄-N), and phosphate phosphorus loads (PO₄-P) for the mid-term scenario period 2041–2070. Compared are the reference and future average model outputs of the 12 main rivers draining to Vistula Lagoon per ENSEMBLE scenario S1–S15. The graphs show the average, minimum, and maximum changes of 15 scenarios in percentage terms as well as the 25- and 75-percentiles.